Max length for data cable?

May 16, 2015
81
C&C 37 28127 Port Madison, Washington
Skippers, marine electricians,
One reason I bought the Vesper Cortex is being able to read sensor data from my legacy RM ST60+ instruments over wifi. I mounted the Cortex hub at the nav station where it's visible and in reach of the masthead antenna coax. This unfortunately means a long run for the data cable aft to the pedestal mounted instruments, 18+ feet. I'm assuming the available 5m Sea Talk cable will splice to the Cortex 0813 GPIO cable (Cortex M1 translates 0183/2000). BUT: Garmin tells me this length will likely result in poor performance.

The hub can move aft in the quarter berth if necessary, but that means adding length to the AIS/VHF coax, power cable, etc. Another possibility is moving the instruments to the cabin bulkhead. Trade-offs, both. Other ideas?

Accessing depth/wind/speed data via wifi would be helpful, but I'm doubting the effort.